This invention is directed to a standing wave charged particle accelerator structure and in particular to an S-band standing wave electron accelerator structure assembled from similar basic components having on-axis coupling cavities.
The need for high efficiency rf accelerating structure operating at room temperature has been fulfilled for certain applications by standing-wave coupled-cavity accelerators, the side-coupled structure described in U.S. Pat. No. 3,546,524 which issued to P. G. Stark on Dec. 8, 1970, being an example. Considerable work has been carried out with respect to side-coupled structures as it has been felt that these structures have the highest possible shunt impedance. Recent measurements have shown that a structure using on-axis coupling cavities has a higher shunt impedance than an equivalent side-coupled structure.
Even though, as with these accelerating structures, the on-axis coupled structure necessarily includes a vacuum tight system with cavity shapes, cooling, and dimensional tolerances determined from constraints associated with desired rf and accelerating properties, its ease of assembly and high efficiency of converting rf power into beam power make it an attractive alternative to the other structures.
U.S. Pat. No. 3,953,758 which issued to Duc Tien Tran on Apr. 27, 1976, described a linear accelerating structure having on-axis coupling. On-axis coupled structures are found to be deficient in that non-axially symmetric modes propagate along the accelerator structure by the coupling slots between the cavities. In addition, cooling systems for the structure are inefficient in that they are not integrated into the structure.